The embodiment relates to a method of configurating a CANopen network, a slave device, and a system for controlling a PLC. In more particular, the embodiment relates to a method of configurating a CANopen network capable of reducing a network load and a transmission delay time, a slave device using the same, and a system for controlling a PLC device.
A control area network (CAN) bus is a two-wire serial communication bus which is an industry standard extensively used for vehicle and industrial control applications, as well as medical equipment, aerial electronic engineering, office automation facilities, consumer products, many other products, and applications. A CAN controller is an independent device configured to interface with a micro-controller. The CAN controller is currently usable in the form of a circuit integrated in a micro-control chip or a module inserted into the micro-controller chip. Since 1986, CAN users (software programmers) have developed a plurality of high-level CAN application layers (CAL) to expand the functions of the CAN while supporting the specification of the CAN with the use of a CAN physical layer and a CAN frame format. A CANopen is one of the CALs, and has been used for network management and monitoring of programmable logic controller (PLC) equipment in various industrial fields while serving as a protocol to support a CAN network.
FIG. 1 shows a CANopen network using a typical CANopen protocol. The CANopen network includes slave devices 11 and 12, and a master device 10 to manage the slave devices 11 and 12.
FIG. 2 is a view to explain the communication procedure between the master device 10 and the first slave device 11, and between the master device 10 and the second slave device 12. FIGS. 3 to 7 are views to explain data transceived in the CANopen network.
As shown in FIG. 2, the master device 10 may be allocated with transmit PDO ports and receive PDO ports to transceive process data objects (POD) based on a CANopen protocol with each slave device. In addition, each of the first slave device 11 and the second slave device 12 may be allocated with transmit PDO ports and receive PDO ports to transceive PDOs with the master device 10.
As shown in FIG. 2, each of the first and second slave devices 11 and 12 receives a PDO from the master device 10 through the receive PDO port thereof, and transmits a PDO to the master device 10 through the transmit PDO port thereof. In this case, each port may be identified through a CANopen object (COB) ID.
FIG. 3 shows a CAN ID serving as a data identifier transceived over a CAN network. The CAN ID contains a 4-bit function code and a 7-bit node ID, and is transceived together with a PDO. The function code may be designated according to data services, and the node ID refers to a number to identify a slave device to which data are transmitted.
FIG. 4 is a view showing the case that the CAN ID is used to identify the PDO. The PDO may be divided into a transmit PDO and a receive PDO. The transmit PDO is transmitted by the slave device, and the receive PDO is received by the slave device. The CAN ID corresponding to each PDO may contain a related function code according to transmission and reception states. The CAN ID for the PDO having a specific function code may contain an intrinsic CAN ID having the form of combination with the node ID.
FIGS. 5 and 6 show the range of indexes and a sub-index allowable for a PDO transceived over the CANopen network. Each index refers to a service (transmission or reception) of a communication protocol for the service of a PDO. Each sub-index may refer to the value of a COB ID serving as an identifier for a destination node or a destination device, to which a PDO is transmitted, and constituting the PDO. FIG. 7 shows the typically defined standard of COB IDs of transmit and receive PDOs
Each of the slave devices 11 and 12 over the CANopen network established according to the COB ID standard receives PDO setting information corresponding to each of the slave devices 11 and 12 before communication is made between the slave devices 11 and 12 and the master device 10. A data frame is transceived between the slave devices 11 and 12, and the master device 10.
However, in the typical CANopen network, each of the slave devices 11 and 12 is set to make communication with only the master device 10. Accordingly, when one slave device 11 must transmit data to another slave device 12, the number of times of frame transmission is significantly required, so that transmission time is significantly spent.